Process of improving carbon black



Patented Dec. 29, 1936 I o I l I UNITED STATES PATEN'I OFFICE,

2,066,274 PROCESS OF IMPROVING CARBON BLACK I Walther H. Grote, Charleston, W. Va., assignor to United Carbon Company, Inc., a corporation 7 of Maryland No Drawing. Application January 19, 1934,

Serial No. 707,411 DEC 1 9 1939 6 Claims. (Cl. 134-60) This invention relates to a. process for making an initial color value of 225 to an oil adsorption. an improved carbon black characterized by a low factor of 175, I find that by subjecting a three oil adsorption factor, improved dispersibility and pound charge of such black to an attrition period particular adaptability for use as a color and of ten hours at 800 F. in a laboratory mill (size reinforcing agent in rubber, plastics, lacquers, 10" x 18") running 50 R. P. M., satisfactory repaints, enamels, inks and the like. sults may be obtained. While attrition at or- I As is well known by those familiar with the dinary temperatures would destroy the color art the oil adsorptive capacity of carbon blacks value of such black I find that under elevated as a general rule increases proportionately" to temperatures this effect is'greatly minimized.

10 their color values. For obvious reasons a lower In the example cited above the initial color value 10 oil adsorption factor, if it could be produced of 225 is, for instance, only reduced to 220. This without considerable decrease in color, would is especially the case if the treatment is acbe extremely desirable and such a result has long complished in an atmosphere of inert gas such as been sought after in the art. carbon dioxide (CO2).

The oil adsorption factor is a familiar index of I have found that the carbon black may be 15 pigment evaluation and may be determined acsubjected to ball milling at a temperature of cording to the method of the A. S. .T. M. from 400 F. to 800 F. for periods varying from (D281--28T) in the following manner. One gram 5 to 15 hours to produce a highly improved carof the air dried sample is placed on a glass plate, bon black as regards reduced oil adsorption, and

20 refined raw linseed oil is added, drop by drop, the carbon black will have a color value of 200 20 from a volumetric burette until by thorough inor better. Milling for five hours gives from corporation with the black by means of rubbing to as much improvement as is' produced by with a steel spatula, a stiff putty-like paste is continuing the milling 15 hours. The oil adsorpproduced which does not break or separate. The tion decreases rather rapidly during the first quantity of oil required for the purpose being few hours of milling, and later the proportionate r then read on the burette and the pounds of oil decrease per hour becomes less, until after fifteen required to wet 100 pounds of black calculated. hours of continuous operation further milling My invention provides a process resulting in an produces only a relatively small decrease in oil improved product in which the degree of selective adsorption per hour. I have further found that adsorption of the individual particle is greatly while the'color loss is progressive during the millreduced without detriment to the other piging, the net loss is slightwhen the temperature mentary qualities. of the carbon black is maintained at least at In carrying out my invention I subject carbon 800 F. I have further found that a slow speed black in its natural fine state of subdivision to of the ball mill seems to give the best results.

attrition under controlled temperature, prefer- It should also be noted that while CO2 is the i ably in a non-oxidizing atmosphere, for example, most practical gas to use to provide an inert atin a ball mill provided with means of heating the mosphere, any non-oxidizing gas such as nitrocharge and maintaining it at predetermined gen may be used.

temperatures for prolonged periods. The balls I have also found that carbon blacks so treated I 40 employed for this purpose are preferably case exhibit greatly improved dispersing qualities 40 hardened steel balls not exceeding inch in wh n admixed to rubber, plastics, l c r diameter. paints, enamels, inks and the like.

The quantitative reduction of the oil adsorp- Since carbon black particles are of colloidal tion factor, achieved by the improved process, dimensions it is assumed that the attrition does depends somewhatbn the initial oil adsorption not appreciably aifect the particle size of the 45 factor prior to treatment.' The higher the initial material, but merely changes the surface confactor, the greater will be the proportionate redition of the individual particle. The exact duction, although several factors entering into effect on the particles accomplished by this the process may be varied so as to get different treatment is not yet definitely known, but it is results. Among these factors are the time of believed that by this treatment the electrical my treatment, speed of the machine, volume of charges upon the colloidal particles are changed, charge, temperature control and atmospheric causing a coalescence, and effecting a reduction medium employed. of the specific surface and/or a change in the For example, if I intend to reduce an oil adsurface tension of the particles thereby decreassorption factor of 220 of a carbon'black having ing their oil adsorptive capacity. 55

' Having described my invention and explained the operation thereof, I-wish it to be understood of my invention without departing from the,es-'

rential principle thereof,

I.claim: 1. The process of improving carbon black by reducing the oil adsorbtion without substantially lowering the tinctorial value of the carbon black,

which comprises subjecting the same to attrition 'in a non-oxidizing atmosphere at elevated temperatures.

2. The process of improving carbon black'by' reducing the oil adsorbtion without substantially lowering the tinctorial value of the carbon 'black, which comprises subjecting the same toattrition in an inert atmosphere at a temperature of above 400 F.

3. The process of improving carbon black by reducing the oil adsorbtion without substantially lowering the tlnctorial value oi! the carbon black, which comprises subjecting the same to attrition for irom about to 15 hours, in an inert atmosphere at elevated temperatures. 1

4. The process of improving carbon black by reducing the oil adsorbtion without substantially lowering the tinctorial value oi the carbon black, which comprises subjecting the same to-attrition in an atmosphere of CO: for about hours at a temperature of about 800 1" 5. The process of improving carbon black by reducing its oil adsorption value without substantially reducing its color value, which comprises subjecting the said carbon black to attrition in a nomoxidizing atmosphere where no chemical reaction takes place and while the carbon black is at a temperature within the range from about 400 F. to about 800 1''. for from 5 to hours 6. The'process of improving carbon-"blackby'." reducing its oil adsorption valuevtromtm to 175 4 without substantially reducing its tinctorial value, which comprises subjecting the said carbon black to attrition in a non-oxidizing while the carbon black is heated to a temperature 0! about 800'F. for about 10 hours.

WALTHER n. cmo'rm. 

